Sleep spindle and slow wave activity in Bipolar Disorder: preliminary observations from a high–density EEG study

Introduction Recent research on Schizophrenia (SCZ) suggests that reduced sleep spindle and slow wave density could be particularly informative of underlying thalamocortical and cortical synchronization mechanisms and dysfunctions. Although sleep disturbances are also highly prevalent across all stages of Bipolar Disorder (BD), the objective evaluation of sleep macrostructure and microstructural oscillatory activity remains understudied in this population. Objectives We aimed to investigate sleep EEG activity in BD, with a focus on sleep architecture, sleep spindles and slow waves. Methods We recorded high-density EEG (64–channel BrainAmp, Brain Products GmbH, Germany) during sleep in 18 euthymic patients with BD and 18 age/gender-matched healthy control (HC) subjects. After sleep scoring and EEG artifact rejection, several parameters of sleep spindles (12-16 Hz), including density and amplitude, and slow waves (0.1-4 Hz) were identified for the first cycle of sleep using automated algorithms and compared between groups using non-parametric statistics. Results BD subjects showed significantly higher Wake After Sleep Onset and lower Sleep Efficiency (Table 1). Total (12 - 16 Hz), slow (12 - 14 Hz) and fast (14 - 16 Hz) sleep spindle parameters of density (Image 1) and amplitude did not differ significantly between groups. On the other hand, slow wave density was reduced in a large frontal cluster of electrodes in the BD group (Image 2).Table 1 BD (n = 18) HC (n = 18) Difference (p value) WASO (min ± sd) 140,61 ± 74,23 84,34 ± 59,84 0,017 Sleep efficiency (% ± sd) 72,47 ± 14,33 82,43 ± 11,58 0,028 Image: Image 2: Conclusions The absence of sleep spindle deficits in the BD group suggests that the systems involved in generating and maintaining these thalamocortical oscillations are presevered during periods of clinical stability in Bipolar Disorder. Conversely, reduced sleep slow wave density points to an altered cortical synchronization, which might represent a common neurophysiological feature shared with Schizophrenia. Further research is needed to confirm these preliminary observations in all–night recordings and with a direct comparison of larger cohorts of patients with both diagnoses. Disclosure of Interest None Declared

Introduction: The existence of a clinical entity on the spectrum of mood disorders characterized by the occurrence of manic episodes without major depressive episodes (Unipolar Mania, UM) is largely debated. Although not classified nosologically, the studies exploring this topic have suggested that UM might differ from bipolar disorder with a manic-depressive course (md-BD), in terms of several clinical characteristics. Individuals with UM might represent a subpopulation with specific clinical profiles and unmet care needs, requiring personalized treatments, as compared with those suffering from md-BD. Objectives: To identify clinical factors associated with UM, as compared with md-BD. Methods: We performed a systematic review and meta-analysis of observational studies according to the MOOSE guidelines. We searched for articles indexed up to July 2022 in the main electronic databases. We conducted random-effects meta-analyses of the association between UM and relevant correlates, using odds ratio for categorical variables and standardized mean difference for continuous variables. Results: Based on data from 21 studies meeting the eligibility criteria, we found that individuals with UM, as compared with md-BD, were more likely to be males (p = 0.007) and to have an earlier age at onset (p = 0.020). Moreover, UM was significantly associated with a higher number of hospitalizations (p < 0.001), the occurrence of psychotic features (p < 0.001), as well as hyperthymic temperament (p = 0.012). Finally, subjects with UM were less likely to report a family history of depression (p = 0.006) and a personal history of suicide attempts (p < 0.001).
Conclusions: Our work supports the hypothesis that UM might represent a distinctive diagnostic construct, with peculiar clinical correlates. Additional research is needed to better differentiate UM in the context of affective disorders.

EPP0791
Sleep spindle and slow wave activity in Bipolar Disorder: preliminary observations from a highdensity EEG study Introduction: Recent research on Schizophrenia (SCZ) suggests that reduced sleep spindle and slow wave density could be particularly informative of underlying thalamocortical and cortical synchronization mechanisms and dysfunctions. Although sleep disturbances are also highly prevalent across all stages of Bipolar Disorder (BD), the objective evaluation of sleep macrostructure and microstructural oscillatory activity remains understudied in this population. Objectives: We aimed to investigate sleep EEG activity in BD, with a focus on sleep architecture, sleep spindles and slow waves. Methods: We recorded high-density EEG (64-channel BrainAmp, Brain Products GmbH, Germany) during sleep in 18 euthymic patients with BD and 18 age/gender-matched healthy control (HC) subjects. After sleep scoring and EEG artifact rejection, several parameters of sleep spindles (12-16 Hz), including density and amplitude, and slow waves (0.1-4 Hz) were identified for the first cycle of sleep using automated algorithms and compared between groups using non-parametric statistics. Results: BD subjects showed significantly higher Wake After Sleep Onset and lower Sleep Efficiency (Table 1). Total (12 -16 Hz), slow (12 -14 Hz) and fast (14 -16 Hz) sleep spindle parameters of density (Image 1) and amplitude did not differ significantly between groups. On the other hand, slow wave density was reduced in a large frontal cluster of electrodes in the BD group (Image 2). Image: Introduction: The definition of mixed states has been changed over the years, leading to substantial heterogeneity and inconsistencies across studies, and thus limiting the understanding of this phenomenon. Given the limited data available after the introduction of the DSM-5 mixed features specifier (MFs), we conducted a cross-sectional study evaluating MFs in individuals suffering from affective disorders, i.e., major depressive disorder (MDD) or bipolar disorder (BD).
Objectives: The aim of this study is to evaluate rates and correlates of MFs in a consecutive sample of inpatients with mood episodes. Methods: We included adults consecutively admitted to our inpatient mental health unit with a current manic episode (ME) or major depressive episode (MDE). DSM-5 criteria were used to assess the occurrence of MFs. Young Mania Rating Scale (YMRS) and Montgomery-Åsberg Depression Rating Scale (MADRS) were used to assess the severity of the mood episodes. We used the Kemp Compliance Rating Scale to assess medication adherence.
Results: A total of 285 individuals were included (mean age AE SD: 48.3 AE 17.9; M/F ratio: 2/3). Among them, 94 (33.0%) were in a ME and 191 (67.0%) in a MDE. Forty individuals (14.0%) exhibited MFs. We found that MFs were significantly more frequent in participants with a diagnosis of BD (p<0.001) and during a ME (p=0.006). In addition, study participants with MFs had lower medication adherence at hospital admission (p=0.008). Finally, individuals with ME and MFs had lower YMRS scores than those without MFs (p<0.001), and, similarly, those with MDE and MFs had lower MADRS scores than those without MFs (p<0.001).
Conclusions: Considering DSM-5 classification, we found that MFs are a phenomenon strongly linked to BD. While the symptom severity of the prevalent polarity tends to be lower in episodes with MFs, the reduced adherence may be suggestive of a more complex clinical management requiring specific treatment approaches.

EPP0793
The Role of The Predominant Polarity on Neurocognitive and Social Cognitive Dysfunctions in Patients with Bipolar Disorder E. Atay 1 *, C. Ermis 2 and E. Ozmen 1